设直线AC的方程为ky=x-p/2（k≠0）联合抛物线y^2=2px消去yx^2-(1+2k^2)px+p^2/4=0xA+xB=p^2/4 依据抛物线的特性AF=xA+p/2；BF=xB+p/2(xB+p/2)/p=CB/CF=2/3∴xB=p/6xA=3p/2AF=3p/2+p/2=2p=3抛物线方程y^2=3x
